Grate bar



'l 10 venting the grate 40 dinal portion into .5 the sake ofsustaining Patented Feb. 14, 1928.

:FRANK A. mnnnnwnm), 'or omesso HEIGHTS, ILLINOIS.

anun BAB,

Apnueanon mea April a1,

This inventionrelates to bars to be assembled in the development of a grate upon which to burn fuel, roast ore, or carry on other industrial processes involving the heating of materials to high temperatures simultaneously with thepassage of air or gases through the grate.

ln all processes of the kind referred to, great difficulty has been encountered in prebars from becoming excessively Warped, and even cracked and fractured, by stresses resulting Jfrom excessive localized thermal expansion and con traction. ln any solid or rigid metal inember, such as an ordinary cast grate bar, the production of limited hot or cold areas will result in a corresponding expansion orv con traction at the particu ar point involved, and if this expansion or contraction is of such an extent that it exceeds the elastic limit of the material, a permanent set, either in contraction or expansion, is produced. In most cases, stresses in excess of the elastic limit, and which are alternately stresses ot compression and tension, will be produced by each temperature fluctuation. A suffi-V cient nnrnber of these stress reversals will cause cracking at high tern eratures, just as alternate stresses produce atigue failures in metals at ordinary temperatures. Morcover, if the grate is not entirely rigid, it will attempt to adjust itself to the dimensional changes referred to by warping or bending from its original shap. Many attempts have' been nitide to moet the problem presented by the conditions above referred to. lt has been proposed to subdivide the lateral portions of the grate bars on opposite sides oi a middle longitutransversely extending ngerdilre projections, or in such a manner as to develop interrupted margins which prevent transmission of stresses of expansion and contraction longitudinally of the 4K5 bar, and it has even been proposed to connect up the outer ends of these lateral portions ofthe bar impairs or groups and developso-called parallelograms or rectangularor diagonally designed frame 'work for them. But none of the attempts `-heretofore made to meet the diiculty, so forv as I am aware, have been successful because even where transversely me. serial no. 193,657.

extending lin er-like subdivisions of the shelves have en joined by longitudinally extendmg integral portions, the fingershave been connected in such large groups orelse the thickness of the fingers were so great, compared with their length as to defeat the Object of relieving the middle longitudinal portion of the grate bar from stresses; and oven when the fingers were connec in pairs, fingers of a pair were so ,widely spaced that there was too great anopportunity for difference in temperatures between them; longitudinal expansionof one relatively to the other'acted upon the other through excessive leverage of the long con-v necting portion, thereby producing objectionable transverse-stresses in the cooler finger; and the excessive length of the connect- A ing portion, hy its own expansion, introduced objectionable transverse stresses in the fingers which it connected; and thus the design failed to insure the results which are the aim of my invention.

Ihe resent invention proceeds uponthe 'princip e of so designing, spacing, and connecting up the outer ends of ad3acent subdivisions or linger-like portions of the lateral shelves of a grate bar, that these subdivisions or portions, hereinafter referred to as fingers, .will be connected onl in pairs; While designed with any desiredY de th to insure vertical-sustention of their loa they will be very much greater in length than in; width; they will be spaced apart a' distance substantially less than their width and very greatlyvless than their length; and the por tions which connect their outer ends will, by

reason of the reduced spacing of the fingers,

be so short that differential longitudinal expansion in the connected lingers, which is necessarily reduced by their closeness t0- gether, will be transmitted through such a shortleverage as to be largely absorbed by a component of longitudinal tension'as well as transverse tiexure in the cooler fingers; moreover, the thickness of the portion which .connects the outer ends of the fin ers is eater than the space which ity bri ges; a substantial advantage incident to the expedient arising from the fact that it involves a closeness of spacing of the fingers or subdivisions whiclrrenders the bar peculiarly well adapted for sintering or roasting ores.

The invention `is.-realikfrmtl by,, lransversely slotting the longitudinally extending llie'lves which project laterallfr'oin opposite sides of a middlesupportmg spine, thereby de veloping closely spaced fingers and preventn ing development of objectionable stresses trom localized expansion or contraction of theiingers; the fingers bein united in pairs by connecting okes integra with their outer ends, and t ese connecting yolres having a dimension transverse to the bar, or in the direction of the length of the iingers, which is large relatively to the space which the yoke bridges7 so that differential expansion or contraction of the two connected fingers,

`instead of developing serious stresses in the lconnecting yoke, Will be absorbed 1n longi tudinal elasticity as well as transverse resiliency or iexing of the fingers themselves; and Will have insuficient capacity to seriously stress the middle member or spine; moreover, the pairs of connected fingers on one side are offset longitudinally of the bar relatively to the pairs on the other side, so that the distance from an open slot on one side to an open slot on the other side is at a substantial angle to the transversediniension of the middle member, and therefore offers much'greater resistance to fracture of the middle member.

The preferred embodiment of the invention is illustrated in the accompanying' drawing, in \vhich-- Figure 1 is a top Yplan View of a gratey bar embodying in its construction the several features of the invention.

Figure 2 is a Side elevation of the same.

Figure 3 is an end view; and

Figure il is a section on the line 4X-lx of Figure 1, but on an enlarged scale` l represents the middle member or spine of the bar, which is designed with a deep sustaining flange la on its underside, and 2 represent the longitudinally extending shelves laterally disposed Ato and integral with the spine l and affording a main supporting area of the bar. The shelves 2 are subdivided by transverse slots 8 and 3 into a. seriesI of fingers 4, so that there can be no stresses dueto expansion or contraction in the direction of the length oi the shelves at their outer margins, or any serious differential in dimension developed between the cuter portions of the shelves and the middle sinstaiuing member, as in grate bars With uninterrupted marginalportions. The slots la are closed in by yokes 5 integral with the outerends of adjacent fingers and joining together the ingers in pairs so aste render the lingers mutually sustaining; but the-"1e closed slots are quitek narrow in order that the dimension of the connecting yokes in the bridging directionl may be short, and the dimension transversely to the bar rela.-

ifelv lxrge, and thereby cause stresses developed by unequal expansion or contraction of tvvopconnected lingers to be absorbed in the fingers themselves as ilexing influences,

'and reduce to a minimum transverse stresses on the middle member or spine. Moreover, the pairs ot' connected lingers on one side are oiset in the direction ot' the length o the bar relatively to those on the other side so that the enclosed slots 3 on one side, in the preferred embodiment, are in alignment with the open slots 3 on the other side; and for this reason, the open slots 3 are of the same Width as the enclosed slots. In other Words, in order to maintain symmetry of de sien on both sides 'ot the middle, and insure dissipation of stresses throughout the bar, the fingers are all closely spaced, and all the slots are narrow. A substantial advantage arising from the narrowness of slots is that the bar is particularly adapted to serve as a member of a grate used for roasting or sintering ores, although it is not restricted in its usefulness to this purpose.

I claim.:

l. A grate bar, comprising a middle longitudinal sustaining spine, and broad longilil tudinally extending shelves laterally related 'i to and integral with said spine; said shelves being slotted transversely, thereby interrupting thermally developed stresses in the shelves in the direction of the length of the bar; and subdividing each shelf area into a series of closely spaced fingers projecting from the spine; said fingers being united in pairs by connecting yokes integral with their outer ends; said connecting yokes having a dimension transverse to the bar which is greater than the Width of the slots 'which they bridge; the Width of the fingers bein greater than the Width of the said slots, and the length of the fingers being materially greater than their width.

2. A grate bar, comprising a middle longitudinal sustaining spine, and broad long1- tudinally extending shelves laterally related to'and integral with said spine; said shelves being composed ot transversely extending fingers of substantial width connectedL together at their outer ends in pairs, With the fingers of each pair i dependent of and :tree from expansional in uence over the negers of the other pairs; the lingers of each pair being spaced apart a distance materially less than the Width of a finger, and the length of the fingers being materially .greater than their Width.

3. A grate bar, comprising a deep middle longitudinally extending sustaining spine, and broad longitudinally extending shelves laterally related to and integral with said spine; each shelf being subdivided into a series of fingers lby uniformly spaced narrow transverse slots, the ngers'being united in pairs, and the slots between the fingers of the several pairs being lenclosed by yokes of `metal integral withV the outer ends of the the enclosed .slots on one side of the spine fingers; the slots between the several .pairs being in alignment with' the open slots on being left open nt their outer ends; the slots the other sidethereof. 10 `between the fingers of each pair being ma- Signed at Chicago, I1linois, this 14th day 5 terially less in width than 4the width of said of April, 1926. l

fingers, and the length of the finger being v materielly greater than their width; and FRANK-YA. FAHRENWALD. 

